Threshold behaviour in steep alluvial streams: key variables and geohazards

陡峭冲积流的阈值行为：关键变量和地质灾害

• 批准号: RGPIN-2015-05017
• 负责人: Eaton, Brett
• 金额: $ 1.6万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=678909
• 关键词: Threshold; behaviour; steep; alluvial; streams

While it is well known that river systems respond to changing environmental conditions such as urbanization, the construction of hydropower dams, and climate change, the tools available to predict the nature and magnitude of such responses are limited. On the one hand, we have generic conceptual models that describe the typical responses that can occur in response to some hypothetical change, but these models seldom account for the particular configuration of a given river system and often identify more than one potential response, leading to vague and sometimes contradictory predictions. On the other hand, we have detailed numeric models that simulate the physics of water flow and sediment transport of the individual sediment grains in a river using the laws of physics; these models seldom consider the relevant ecological processes that influence channel response, require detailed (and expensive) input data, and are unable to predict the long-term effects occurring over several decades or centuries. A kind of hybrid computer modelling approach (called cellular automata models, or CAMs) has emerged to bridge the gap that is based on using rules describing stream response that are based on the behavior of large-scale features such as pools and bars, but the assumptions and simplifications required to construct them introduces significant uncertainty with respect to their accuracy. My research group will study the physics controlling the behavior of these larger features in the laboratory and in the field, in order that we may improve the physical basis for predicting how streams respond to environmental change, in terms of both channel characteristics and the available physical habitat for fish. Our results may be incorporated into existing CAMs or into other numerical modelling frameworks for predicting channel response at spatial and temporal scales relevant to environmental managers. The specific focus of a large part of the proposed research is the nature of the change in sediment transport dynamics that occurs when steep, mountainous streams experience rare floods, erode their banks, and change their characteristics significantly. Not only do such events represent significant hazards to human life and infrastructure, they may be the primary means by which such channels adjust their boundaries, unlike larger, lower gradient streams which are subject to less variable stream flows, and which routinely undergo relatively minor channel changes. Since many communities in the Canadian Cordillera are built in part upon sediment deposits associated with such streams, it is important that we improve our understanding of the ways in which they behave, how they are likely to respond to various environmental changes, and how the hazards associated with their natural dynamics may best be mitigated.

虽然众所周知，河流系统会对不断变化的环境条件作出反应，如城市化、水电站大坝的建设和气候变化，但可用于预测这些反应的性质和程度的工具有限。一方面，我们有通用的概念模型，描述了一些假设的变化可能发生的典型反应，但这些模型很少考虑特定的配置一个给定的河流系统，往往确定一个以上的潜在响应，导致模糊，有时相互矛盾的预测。另一方面，我们有详细的数值模型，模拟水流的物理和泥沙输运的单个泥沙颗粒在河流中使用的物理定律，这些模型很少考虑相关的生态过程，影响通道的响应，需要详细的（和昂贵的）输入数据，并无法预测发生在几十年或几个世纪的长期影响。一种混合计算机建模方法（称为元胞自动机模型，或CAM）已经出现，以弥合差距，该差距是基于使用规则描述流响应，这些规则是基于大规模特征（如池和酒吧）的行为，但构建它们所需的假设和简化引入了显着的不确定性。我的研究小组将在实验室和野外研究控制这些较大特征行为的物理学，以便我们可以改善预测河流如何响应环境变化的物理基础，包括河道特征和鱼类可用的物理栖息地。我们的结果可以纳入现有的CAM或其他数值建模框架，用于预测与环境管理者相关的空间和时间尺度上的通道响应。拟议研究的一大部分的具体重点是发生在陡峭的山区河流经历罕见的洪水，侵蚀他们的银行，并显着改变其特性时，泥沙输运动力学的变化的性质。这类事件不仅对人类生命和基础设施构成重大危害，而且可能是这类河道调整其边界的主要手段，这与较大、较低梯度的河流不同，这些河流受到较少变化的河流流量的影响，并且通常会经历相对较小的河道变化。由于加拿大科迪勒拉山脉的许多社区部分建立在与这些溪流相关的沉积物上，因此我们必须提高对它们行为方式的理解，了解它们如何应对各种环境变化，以及如何最好地减轻与自然动态相关的危害。